The invention relates to a coupler for connecting together the adjacent straight ends of two clay, concrete, metal or similar pipes.
One long-standing object in the pipe industry, and particularly the clay pipe industry, has been the elimination of the clay bell end of the pipe which receives the straight end of another pipe in a male-female connection. Formation of bells on clay pipe requires an additional manufacturing step and also provides an inherent weak point for breakage of the pipe either during manufacture, or, even worse, after installation. In addition, the bells make the pipes difficult to stack and reduce the number of pipes which can be fired at any given time, in contrast to pipes having straight ends.
One approach which has been successfully employed is to form a separate bell on one end of a piece of straight clay pipe or the like by winding fiberglass about a mandrel and about the end to form a non-clay socket which can then be conventionally cured. The patent to Gray, U.S. Pat. No. 4,024,006, describes one such technique and structure in detail.
Another approach in the art has been to provide a separate coupling which is placed between the straight ends of adjacent pipes at the time of installation in the ground. Rigid cylindrical tubes of metal and various types of plastics have been tried. The difficulty with rigid tubes is that they do not permit shifting and movement of the pipe which often takes place as the ground settles. The result is that the coupler breaks or the pipes break, creating a leak either into or out of the pipe.
Alternatively, the coupler can be a flexible cylindrical tube made of rubber or similar material. The difficulty with such a flexible tube is in achieving a proper seating and sealing and in providing sufficient rigidity to adequately couple together two pipe ends.
Several attempts have been made in the past to in part combine rigid and flexible characteristics in a single coupling device. The patent to Havell U.S. Pat. No. 3,558,164, for example, describes a pipe coupling with an elastomeric cylindrical tube mounting a central pipe stop of rigid material. The elastomeric tube is wound about its entire length with fiberglass which provides a restraining sheath.
The patent to Viazzi U.S. Pat. No. 3,667,782 describes another coupling with a sleeve of material which can be resiliently deformed to seal together two straight pipe ends.
The patent to Garrett, U.S. Pat. No. 3,394,952, describes yet another joint of elastomeric material with central rigid portions extending down between the pipe ends, lips at either end for sealing and bands which compress the lips against the pipe to effect a seal.
The present invention relates to a coupler which combines a flexible sealing member with at least three rigid outer rings and one rigid inner ring, the resulting combination providing particularly satisfactory results and responding to all of the problems which have been encountered before with separate pipe couplers.
The present invention shares with couplers of the type described in the above-mentioned patents independence of the pipe itself and thus of the pipe manufacturing process. The coupler can be made at a location different from that where the pipe is made, and can be salvaged in the event of pipe breakage. The coupler can be installed on one end of the pipe at the pipe-producing plant or all the installation can take place at the time of installation. The coupler can be installed on field cut pipe as well as pipes that have formed radii or bevels on the pipe ends.
The present invention is particularly advantageous, however, in that the coupling has no loose parts that can be lost or left off during installation and requires no extra tools other than a lubricant to install. The coupler described in the patent to Garrett, for example, uses two bands on the ends thereof for compressing the elastomeric material and to thus effect the seal. However, the bands are conventional clamping elements and thus are external to the device and require special tools for installation.
The coupler of the present invention includes a generally cylindrical flexible sealing member with a central circumferentially extending groove on the outside periphery thereof. A similar groove extends circumferentially on the inside periphery opposite the outer groove mounts a rigid center ring which preferably has a stop surface extending radially inward for positioning pipes to be coupled together. Two pairs of support grooves flank the central groove on the outside of the flexible sealing member adjacent the ends thereof. Unitary sealing lips are provided on the inner surface of the flexible member between the pair of support grooves and opposite a band on the outer surface.
The specific construction will meet double A.S.T.M. requirements for clay pipe joints for infiltration-exfiltration, shear load and misalignment. Further, the combination of rigidity and flexibility permits the coupler to couple pipes which are substantially misaligned. This is particularly important since misalignment can take place during or after installation. Some variation in or out-of-roundness of pipes can be accepted because of the combination of rigidity and flexibility at the right places.
Other objects and purposes of the invention will be clear from the following detailed description of the drawings.